1. Field of the Invention
The present invention relates to a power supply terminal assembly for supplying electric power to a board, and more particularly to a power supply terminal assembly for use on a back wiring board (BWB) of a communication device.
2. Description of the Related Art
In recent years, communication systems have been required to have a higher-density structure, a larger information-transmitting capacity, and more sophisticated capabilities, due to an upsurge in the use of data communications and the like.
Under the circumstances, each communication device tends to consume an increased amount of electric power and hence is required to be capable of handling a large current.
Further, back wiring boards (BWBs) of the communication devices keep on becoming highly multilayered, and with an increase in the layers of their multilayered structure, they are becoming thicker and thicker.
Connectors for supplying electric power to BWB are mostly of solderless connection type in which connection are established by press-fitting in a matched impedance configuration so as to allow high-frequency signals to pass therethrough.
Conventionally, electric power is supplied to a BWB based on the following constructions:
In a first construction, electric wires each having one end thereof soldered to a power terminal are inserted into respective through holes formed through a BWB for soldered connection between the electric wires and the BWB.
According to this construction, power supply capacity is determined depending on the number of the electric wires and a diameter of each electric wire which is dependent on current capacity of a power source, so that it is required to increase the number of electric wires or the diameter of each electric wire so as to make the BWB capable of handling large currents.
In a second construction, electric power is supplied through press-fit power connectors. In this case, the press-fit power connectors are embedded in a BWB, and a power source side is also provided with connectors.
According to this construction, power supply capacity is determined depending on the number of the press-fit power connectors and that of pins of each press-fit power connector, so that it is required to increase the press-fit power connectors or the connector pins in number so as to make the BWB using this construction capable of handling large currents.
A third construction is one in which a plurality of press-fit terminals are mounted separately. This construction will be described below with reference to FIGS. 6(A) and 6(B). FIGS. 6(A) and 6(B) show the construction of a press-fit terminal employed in this construction.
The press-fit terminal 10 shown in FIGS. 6(A) and 6(B) has a body 11 bent into a U-shape and having opposite ends thereof formed with comb teeth-shaped press-fit terminal pins 12a to 12e. Further, at a center of a flat central portion of the body 11, there is formed a through screw hole 13 into which a screw 1 is screwed. Reference numeral 2 indicates a sectional view of the press-fit terminal 10 taken on line 6(B)--6(B) in FIG. 6A.
Next, a procedure of mounting the press-fit terminal 10 constructed as above onto a BWB will be described with reference to FIGS. 7(A) and 7(B). FIGS. 7(A) and 7(B) show a plurality of press-fit terminals mounted in the BWB. FIG. 7(A) is a plan view, while FIG. 7(B) is a sectional view taken on line B--B of FIG. 7(A).
As shown in FIGS. 7(A) and 7(B), in wiring by the use of the press-fit terminals 10a to 10e, the press-fit terminal pins 12a to 12e of the press-fit terminals 10a to 10e are each separately inserted into a pair of through holes formed through the BWB 20 and fixed thereat. Then, the screws 1a to 1e are screwed respectively into the screw holes 13 (see FIGS. 6(A) and 6(B)) of the press-fit terminals 10a to 10e via crimp terminals 3a to 3e (appearing in FIG. 7(B)) for electric wires.
Instead of using the crimp terminals 3a to 3e, the wires may be wound around the screws 1a to 1e, respectively, connection to the press-fit terminals 10a to 10e.
According to the third construction, current capacity depends on the number of the press-fit terminal pins and the diameter of each connectable wire.
However, the first construction requires a structure for mounting of the mechanism. Further, when the apparatus using the BWB consumes a large amount of electric power, it is required to connect a plurality of electric wires to one terminal or use wires having a large diameter, which degrades manufacturing efficiency. Further, when the electric wires are increased in number, it is also required to increase mounting space. Moreover, an increase in thickness of the BWB can cause defective soldered connections.
The second construction using press-fit power connectors is mechanically retained by connectors, so that it is inferior in ruggedness. In addition, since this construction is a connector-type, erroneous wiring can be carried out when the number of electrodes of one press-fit power connector is identical to that of electrodes of another press-fit power connector, and hence voltage-monitoring capability is required for checking the wiring.
As far as the third construction is concerned, the body of each of the press-fit terminals used therein is formed with the screw hole having a female screw thread directly cut therein (e.g. by burring) for connection to an electric wire. The strength of this structure against tightening by a screw is dependent on thickness and material of the terminal itself, so that a small terminal as shown in FIGS. 6(A) and 6(B) is not reliable in strength of its body.
Further, since the terminals are mounted separately in the BWB as shown in FIGS. 7(A) and 7(B), manufacturing efficiency is low. Further, if terminals are arranged close to each other, a feeder to be connected or actually connected to a corresponding one of the terminals can come into contact with an adjacent terminal when it is connected or in the connected state.
Moreover, the screw hole 13 of the press-fit terminal is a through hole. Therefore, so long as a screw 1 having an appropriate length is used as shown in FIG. 8(A), there is no problem. However, as shown in FIG. 8(B), if a long screw if is used, there is a problem that an end of the screw damages the BWB and the terminal falls off the BWB as indicated by reference numeral 3 therein.